Summary of Interactions with Vitamins, Herbs, & Foods

Replenish Depleted Nutrients

Metformin therapy has been shown to deplete vitamin B12,1 and sometimes, but not always,2 folic acid as well.3 This depletion occurs through the interruption of a calcium-dependent mechanism. Supplementation with calcium has reversed this effect in a clinical trial.4 People taking metformin should supplement vitamin B12 and folic acid or ask their doctor to monitor folic acid and vitamin B12 levels.

Metformin therapy has been shown to deplete vitamin B12,5 and sometimes, but not always,6 folic acid as well.7 This depletion occurs through the interruption of a calcium-dependent mechanism. Supplementation with calcium has reversed this effect in a clinical trial.8 People taking metformin should supplement vitamin B12 and folic acid or ask their doctor to monitor folic acid and vitamin B12 levels.

Reduce Side Effects

Metformin therapy has been shown to deplete vitamin B12,9 and sometimes, but not always,10 folic acid as well.11 This depletion occurs through the interruption of a calcium-dependent mechanism. Supplementation with calcium has reversed this effect in a clinical trial.12 People taking metformin should supplement vitamin B12 and folic acid or ask their doctor to monitor folic acid and vitamin B12 levels.

Support Medicine

none

Reduces Effectiveness

Guar Gum

In a small, controlled study, guar gum plus metformin slowed the rate of metformin absorption.13 In people with diabetes this interaction could reduce the blood sugar–lowering effectiveness of metformin. Until more is known, metformin should be taken two hours before or two hours after guar gum–containing supplements. It remains unclear whether the small amounts of guar gum found in many processed foods is enough to significantly affect metformin absorption.

Potential Negative Interaction

In a preliminary trial, administration of Ginkgo biloba extract (120 mg per day) for three months to patients with type 2 diabetes who were taking oral anti-diabetes medication resulted in a significant worsening of glucose tolerance. Ginkgo did not impair glucose tolerance in individuals whose diabetes was controlled by diet.14 Individuals taking oral anti-diabetes medication should consult a doctor before taking Ginkgo biloba.

Explanation Required

Chromium supplements have been shown to improve blood sugar control in people with diabetes.15 Consequently, supplementing with chromium could reduce blood sugar levels in people with taking metformin, potentially resulting in abnormally low blood sugar levels (hypoglycemia). While chromium supplementation may be beneficial for people with diabetes, its use in combination with metformin or with any other blood sugar-lowering medication should be supervised by a doctor.

In a study of patients with poorly controlled type 2 diabetes, low blood levels of magnesium, and high urine magnesium loss, metformin therapy was associated with reduced urinary magnesium losses but no change in low blood levels of magnesium.18 Whether this interaction has clinical importance remains unclear.

The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.

Please read the disclaimer about the limitations of the information provided here. Do NOT rely solely on the information in this article. The Aisle7 knowledgebase does not contain every possible interaction.

The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2015.

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use.
How this information was developed to help you make better health decisions.

Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.